Quench hardening of metals with improved quenching medium additive

ABSTRACT

Metals are quench hardened by being heated above the critical temperature and then immersed in a quenching medium containing a calcium petroleum sulfonate having a base number less than 15 and prepared by sulfonating one part by weight of a propanefractionated, solvent-extracted, dewaxed intermediate base bright stock having a viscosity of about 200 to 230 SUS at 210* F. and a viscosity index of at least about 85 with a quantity of sulfonating agent consisting essentially of liquid SO3 dissolved in an inorganic solvent equivalent to from about 0.1 to about 1 part by weight of 20 percent fuming sulfuric acid, at a temperature in the range of about 50* to 200* F.; neutralizing the resulting reaction mixture with at least the minimum required for neutralization of an aqueous slurry of calcium hydroxide; heating the resulting mixture in the liquid phase at a temperature of about 360* to 400* F. for about 10 minutes; and removing water and inorganic solids therefrom to obtain calcium petroleum sulfonate product containing not more than 6 weight percent sulfated ash. This calcium petroleum sulfonate product can be used directly to supply the calcium petroleum sulfonate or the calcium petroleum sulfonate can be extracted from this product and utilized in a more purified form.

United States Patent [72] Inventor Bill Mitacek Bartlesville, Okla. [21] Appl. No. 766,315 [22] Filed Oct. 9, 1968 [45] Patented Sept. 21, 1971 [73] Assignee Phillips Petroleum Company [54] QUENCl-l HARDENING OF METALS WITH IMPROVED QUENCIIING MEDIUM ADDITIVE 9 Claims, No Drawings [52] IU.S.C1 148/18, 148/13.l, l48/20.6, 148/29 [51] Int-Cl C21d1/58 [50] Field of Search 148/29, 20.6,18,13.1

[56] References Cited UNITED STATES PATENTS 2,670,310 2/1954 Freeman 148/18 2,799,606 7/1957 Freeman 148/18 3,135,693 6/1964 Whitney et al... 252/18 X 3,159,510 12/1964 Rozalskyet a1.. 148/29 3,498,850 3/1970 Morton 148/29 X FOREIGN PATENTS 479,069 12/1951 Canada 148/18 697,755 148/29 9/1953 Great Britain Primary Examiner-L. Dewayne Rutledge Assistant Examiner-{3. K. White Attorney-Young and Quigg ABSTRACT: Metals are quench hardened by being heated above the critical temperature and then immersed in a quenching medium containing a calcium petroleum sulfonate having a base number less than 15 and prepared by sulfonating one part by weight of a propane-fractionated, solvent-extracted, dewaxed intermediate base bright stock having a viscosity of about 200 to 230 SUS at 210 F. and a viscosity index of at least about 85 with a quantity of sulfonating agent consisting essentially of liquid S0 dissolved in an inorganic solvent equivalent to from about 0.1 to about 1 part by weight of 20 percent fuming sulfuric acid, at a temperature in the range of about 50 to 200 F neutralizing the resulting reaction mixture with at least the minimum required for neutralization of an aqueous slurry of calcium hydroxide; heating the resulting mixture in the liquid phase at a temperature of about 360 to 400 F. for about 10 minutes; and removing water and inorganic solids therefrom to obtain calcium petroleum sulfonate product containing not more than 6 weight percent sulfated ash. This calcium petroleum sulfonate product can be used directly to supply the calcium petroleum sulfonate or the calcium petroleum sulfonate can be extracted from this product and utilized in a more purified form.

QUENCll-ll HARDENING F METALS WllTH IMPROVED QUENCHTNG MEDIUM ADDITIVE In the quench hardening of metals such as steel, the degree of hardness achieved is dependent upon the time required to cool the metal through the transformation stage. Thus, if carbon steel is quenched from above the critical austenitic temperature of slightly over 1400 F. at a rate so slow, as by air cooling, that the transformation takes place above about 1,000 F., soft pearlite is formed. If the transformation takes place between about 1,000 F. and about 600 F., as when utilizing a straight mineral oil as the quenching fluid, bainite of intermediate hardness is formed. Martensite, the hardest product which can be formed, results when the transformation begins at about 500 F. The lower transformation initiation temperatures are achieved only by very rapid cooling. The ultimate in quenching fluid would be to provide rapid quenching from the moment the steel is immersed to the moment it starts transforming to martensite, and from that point to continue cooling at a slow even rate. The first property is needed so that the softer pearlite or bainite will not form even when the leanest steels are quenched, and the second is necessary to ensure that the martensites will form evenly without cracking or distortion. The use of water as the quenching fluid achieves the fastest quenching rate, but frequently results in cracking or warping. in addition, the use of water has the obvious disadvantage of promoting rust.

It has been suggested that various chemicals, including any of the thousands of organic sulfonates, be added to the quenching oil to increase the quenching rate. Many of these materials have been tried and found to be unsatisfactory.

l have now discovered that a very high quench rate can be achieved while at the same time providing very low staining of the metal, by incorporating into the quench medium prior to the immersion of the metal article therein a calcium petroleurn sulfonate having a base number less than 15 and prepared by sulfonating one part by weight of a propane-fractionated, solvent-extracted, dewaxed intermediate base bright stock having a viscosity of about 200 to 230 SUS at 210 F. and a viscosity index of at least about 85 with a quantity of sulfonating agent consisting essentially of liquid S0 dissolved in an inorganic solvent equivalent to from about 0.1 to about 1 part by weight of 20 percent fuming sulfuric acid at a temperature in the range of about 50 F. to 200 F.; neutralizing the resulting reaction mixture with at least the minimum required for neutralization of an aqueous slurry of calcium hydroxide; heating the resulting mixture in the liquid phase at a temperature of about 360 F. to 400 F. for about minutes; and removing water and inorganic solids therefrom to obtain calcium petroleum sulfonate product containing not more than 6 weight percent sulfated ash. This calcium petroleum sulfonate product can be employed as the additive or processed to recover a more nearly pure calcium petroleum sulfonate. The calcium petroleum sulfonate product is presently preferred, and generally would be employed in an amount in the range of about 0.2 to about 30 weight percent of the quench medium. lt is desirable that the purified calcium petroleum sulfonate or the calcium petroleum sulfonate product be employed in an amount to provide about 0.1 to about weight percent of calcium petroleum sulfonate, based on the quench medium. This particular type of calcium sulfonate product also significantly increases the resistance of the quenching medium to oxidation.

Accordingly, it is an object of the invention to provide an improved quenching process. Another object of the invention is to achieve a rapid quenching of steel while minimizing oxidation and staining. It is also an object of the invention to provide a quenching oil additive which increases the stability of the quenching oil against oxidation. Other objects, aspects and advantages of the invention will be apparent from a study of the specification and the appended claims to the invention.

The calcium petroleum sulfonate additive utilized as a quenching oil additive in the present invention can be prepared in accordance with the disclosure of W. B. Whitney et al., US. Pat. No. 3,135,693, issued June 2, 1964, which is incorporated herein by reference.

The process of the aforementioned Whitney et al., patent produces a concentrate of the additive of the present invenrating of E rnpresentssevere staining m tion, that is, the calcium petroleum sulfonate is generally accompanied by an approximately equal amount, by weight, of a residual unsulfonated product oil. The calcium petroleum sulfonate per se can be isolated or separated from this product oil, by any suitable method or the admixture can be employed. One suitable technique for separating the calcium petroleum sulfonate from concentrate is contacting the concentrate with propane at a pressure of about 600 to 700 p.s.i. g. at a temperature in the range of to F. to extract the unsulfonated oil from the concentrate. Normal butane can be employed as the extracting medium at a pressure of about 400 400 to 500 p.s.i.g. at a temperature of 290 to 305 F. However, this unsulfonated product oil is believed to be a valuable component of the finished quench oil composition and, thus, it is ordinarily not extracted from the sulfonate product. Thus, the calcium petroleum sulfonate product referred to throughout this specification refers to the concentrate product of the Whitney et a1., process which includes this unsulfonated product oil.

The calcium petroleum sulfonate additive of the invention can be utilized in any suitable amount in the quenching oil base, but will generally be employed in an amount to provide calcium petroleum sulfonate in the range of about 0.1 to about 15 weight percent based on the quenching oil base, preferably in the range of about 1 to about 10 weight percent. Where the calcium petroleum sulfonate product, or concentrate, is used, it will generally be employed in an amount in the range of about 0.2 to about 30 weight percent based on the quenching oil base. It is desirable that the calcium petroleum sulfonate additive of the invention have a base number less than 15, and preferably less than 12 to minimize deposits on the metal being quenched.

The quenching oil base can be any suitable known quenching mineral oil or an emulsion of mineral oil and water. Thus, conventional mineral oils including petroleum oil, petroleum oil fractions, and petroleum oil distillates can be used. Refined oils, particularly refined lubricating grade oils, are presently preferred. Mineral oils such as these, and blends of such oils, having a 100 F. viscosity in the range of 50-200 SUS are ordinarily used. If desired, such oils can be emulsified with minor amounts of water.

The improved quenching medium additive of the present invention, being oil soluble, is incorporated into the mineral oil base by simple mixing at any convenient: temperature.

The following examples are presented in further illustration of the invention but should not be construed in undue limitation thereof.

EXAMPLE 1 Three calcium petroleum sulfonates were evaluated using a magnetic quenchometer. in each run a new 41-inch spherical nickel ball was heated to 1,600 F. and maintained at that temperature for thirty minutes and then quenched by immersion in 200 ml., of the quenching oil under test in a magnetic field. When the ball was cooled to 670 (Curie point), it regained its magnetism and was moved by the magnetic field. The time period from the instant of immersion to the instant the 670 F. point is reached in the quench time. The ball was then removed from the quenching oil and the surface deposits removed by rubbing first with a solvent-soaked cloth and then with fine steel wool. The discoloration remaining on the ball after deposit removal is defined as staining. In each run the quenching oil base was a refined Mid-Continent SAE-10 base stock. The conditions and results are recorded in Table 1.

1 Weight percent based on quenching oil base.

2 The degree of staining was evaluated by visual rating using the rating scale pictured in Figure 4 01 High Speed, Bright'Quench 0 11s, presented at. the 17th ASLE annual meeting, May 1962 (Reprint so. 62AM 4B-2). Rating 01A represents an essentially stain-tree condition while a Additive A was a calcium petroleum sulfonate product prepared in accordance with the present invention and contained about 4.8 weight percent sulfated ash, about 0.50 milliequivalents sulfonate per g., a base number of about 8, a viscosity of about 1,400 SUS at 210 F., a flash point of about 480 F., and a water content of less than 0.1 percent. It was prepared by the sulfonation of a petroleum stock of about 200-230 SUS at 210 F.

Additive B was a commercial calcium petroleum sulfonate prepared by sulfonating a petroleum-derived heavy byproduct, obtained from the manufacture of nonbiodegradable detergent propylene tetramer alkylate of benzene, the byproduct having before sulfonation a viscosity of approximately 60-70 SUS at 210 F.

Additive C was a commercial calcium petroleum sulfonate prepared by sulfonating a petroleum fraction having before sulfonation a viscosity of approximately 60-70 SUS at 210 F.

These data show that the calcium petroleum sulfonate of I the present invention provides a faster quenching speed while decreasing the staining of the metal when compared to other conventional calcium petroleum sulfonates.

EXAMPLE ll Evaluations of the oxidation stability of the quenching oils of Runs 2, 3 and 4 were made with the Norma Hoffman test (ASTM D942-50, with a copper wire catalyst to promote oxidation). The results were as follows:

TABLE 11 Pressure Drop. p.s.i.

(a) The evaluations of the quenching oils with additives B and C were stopped at the end of72 hours.

These data show the higher oxidation stability of the quenching oil containing the calcium petroleum sulfonate of the invention over other quench oils with conventional calcium petroleum sulfonates. These tests also show that not all such metal sulfonates are suitable for use in quenching oils and that the sulfonates of the present invention, prepared from 200-230 SUS at 210 F. petroleum stock according to the process of Whitney et al., show surprising utility and ad- 4 vantages in quenching oils as measured in at least three important characteristics of such quenching oils.

Reasonable variations and modifications are possible within the scope of the foregoing disclosure and the appended claims to the invention.

1. In a method of hardening metals which are hardenable by heating and quenching, comprising heating an article of at least one of said metals to a temperatureabove the critical temperature of said at least one of said metals and quenching the thus heated article by immersion in a quenching liquid medium selected from the group consisting of mineral oil, and mineral oil-water emulsions, the improvement comprising incorporating into said medium prior to the immersion of said article therein a calcium petroleum sulfonate having a base number less than 15 and prepared by sulfonating one part by weight of a propane-fractionated, so vent-extracted, dewaxed intermediate base bright stock having a viscosity of about 200 to 230 SUS at 210 F. and a viscosity index of at least about with a quantity of sulfonating agent consisting essentially of liquid S0 dissolved in an inorganic solvent equivalent to from about 0.1 to about 1 part by weight of 20 percent fuming sulfuric acid, at a temperature in the range of about 50 to 200 F neutralizing the resulting reaction mixture with at least the minimum required for neutralization of an aqueous slurry of calcium hydroxide; heating the resulting mixture in the liquid phase at a temperature of about 360 to 400 F. for about 10 minutes; and removing water and inorganic solids therefrom to obtain calcium petroleum sulfonate product containing not more than 6 weight percent sulfated ash.

2. A method in accordance with claim 1 wherein said calci um petroleum sulfonate is recovered from said calcium petroleum sulfonate product prior to the incorporation of said calcium petroleum sulfonate into said medium.

3. A method in accordance with claim 2 wherein the calcium petroleum sulfonate is incorporated into said medium in an amount of about 0.1 to about 15 weight percent based on said medium.

4. A method in accordance with claim 1 wherein said calcium petroleum sulfonate is incorporated into said medium in the form of said calcium petroleum sulfonate product.

5. A method in accordance with claim 4 wherein said calcium petroleum sulfonate product is incorporated into said medium in an amount in the range of about 0.2 to about 30 weight percent based on said medium.

6. A method in accordance with claim 1 wherein said calcium petroleum sulfonate is incorporated into said medium in an amount of about 1 to about 10 weight percent based on said medium.

7. A method in accordance with claim 6 wherein said at least one of said metals is steel.

8. A method in accordance with claim 7 wherein said medium is mineral oil.

9. A method in accordance with claim 8 wherein said base number is less than 12. 

2. A method in accordance with claim 1 wherein said calcium petroleum sulfonate is recovered from said calcium petroleum sulfonate product prior to the incorporation of said calcium petroleum sulfonate into said medium.
 3. A method in accordance with claim 2 wherein the calcium petroleum sulfonate is incorporated into said medium in an amount of about 0.1 to about 15 weight percent based on said medium.
 4. A method in accordance with claim 1 wherein said calcium petroleum sulfonate is incorporated into said medium in the form of said calcium petroleum sulfonate product.
 5. A method in accordance with claim 4 wherein said calcium petroleum sulfonate product is incorpoRated into said medium in an amount in the range of about 0.2 to about 30 weight percent based on said medium.
 6. A method in accordance with claim 1 wherein said calcium petroleum sulfonate is incorporated into said medium in an amount of about 1 to about 10 weight percent based on said medium.
 7. A method in accordance with claim 6 wherein said at least one of said metals is steel.
 8. A method in accordance with claim 7 wherein said medium is mineral oil.
 9. A method in accordance with claim 8 wherein said base number is less than
 12. 